1. Field of the Invention
The present invention relates to a display array and a method for fabricating the same, and in particular, to an active device array substrate and a method for fabricating the same.
2. Description of Related Art
With a rapid progress in science and technology, a demand for displays is increasing along with an advancement of display technology. Conventionally, since cathode ray tubes (CRTs) are fully developed and have extraordinary display quality, the CRTs have played a dominant role in the display market for years. However, the rise of “environmental protection” awareness is against the CRTs due to the CRTs' disadvantages including high power consumption and high radiation, and the limited flattening capability of the CRTs is against the market demands for light, thin, short, small, compact, and power-saving displays. As a result, a thinner and lighter flat panel display (FPD) gradually replaces the traditional CRT, wherein a liquid crystal display (LCD) with great properties of high image quality, high efficiency of space use, low power consumption, and low radiation has become the main trend in the market.
In recent years, a photo sensor is integrated in the FPD in order to enhance the convenience in operating a display interface between a user and the FPD, or to improve the display quality of the FPD. In detail, the photo sensor can be used as an input device of an optical touch panel. When the user touch the optical touch panel with his/her fingers or other articles, the photo sensor integrated in the LCD detects the change in light and output a corresponding signal to perform various functions. Another employment of the photo sensor is to integrate the photo sensor in the FPD as an ambient light sensor, thereby detecting the intensity of the ambient light.
A current and common ambient light sensing technology is to form a p-i-n (P-type doped/undoped/N-type doped) photo sensor on a glass substrate of a display panel through a low temperature poly-silicon (LTPS) process. However, due to the limitation of the process, the p-i-n photo-sensors manufactured by the LTPS technology have a poor quantum effect (i.e. photoelectric conversion efficiency) because of an insufficient thickness of the poly-silicon thin film. In addition, the light from a backlight source directly irradiates the p-i-n photo sensor through the glass substrate and thus affects the photosensitive characteristics of the p-i-n photo sensor, reduces a signal to noise ratio (SNR) of a photosensitive signal, and causes distortion of measurement results.
In other words, a photosensitive material serving as the active layer in the photo sensor has the problem that, even though a voltage is not applied to electrodes on two sides of the photosensitive material, as long as the photosensitive material is irradiated by light, the reliability performance of the photo sensor is affected due to the attenuation of photo current of the photo sensor. Therefore, when manufacturing an active device array substrate having the photo sensor, a patterning process of the photosensitive material and the patterning process of the light-shielding electrode layer adjacent to the photosensitive material are performed by using different photolithography and etching processes, such that the size of the photosensitive material is smaller than the size of the light-shielding electrode layer adjacent thereto. Thus, with respect to the method for fabricating the active device array substrate having the photo sensor, an additional photolithography and etching process is required to form the patterns of the photosensitive material because of the incompatibility between the patterning process of the photosensitive material and the method for fabricating the active device array substrate. Therefore, the fabricating process can not be curtailed to reduce the process cost, which results in lowering the competitiveness of the product.